[bug] UI overlap audit — panels collide on small screens

[kody-w]

Problem

Quest tracker, minimap, kill feed, voice indicator, world populations panel, and universe card overlap on screens < 1440px wide.

Acceptance Criteria

• No panel overlaps at 1280x720
• No panel overlaps at 1920x1080
• Mobile (375x812) shows only essential HUD
• All panels have proper z-index ordering

Echo Level

L5 — spatial rendering fix. Frozen fact: panel content. Enrichable: positions and responsive breakpoints.